执行如下代码，会输出 钢琴：叮咚叮咚 和 吉他：咚咚当当。这体现了面向对象编程的（ ）特性。
class Instrument {public: virtual void play() { cout << "乐器在演奏声音" << endl; } virtual ~Instrument() {}}; class Piano : public Instrument {public: void play() override { cout << "钢琴：叮咚叮咚" << endl; }}; class Guitar : public Instrument {public: void play() override { cout << "吉他：咚咚当当" << endl; }}; int main() { Instrument* instruments[2]; instruments[0] = new Piano(); instruments[1] = new Guitar(); for (int i = 0; i < 2; ++i) { instruments[i]->play(); } for (int i = 0; i < 2; ++i) { delete instruments[i]; } return 0;}